Polyimide precursor, polyimide and their use

ABSTRACT

A polyimide precursor having repeating units of the formula: ##STR1## wherein R 1  is a tetravalent organic group; and R 2  is a divalent diphenyl group, is excellent in image formation and particularly suitable for forming a pattern using an i-line stepper, and gives a photosensitive resin composition by imparting photosensitivity to the polyimide precursor, said photosensitive resin composition being suitable for forming surface protective films for semiconductor devices or interlaminar insulating films for multilayer wiring boards.

This application is a Divisional application of application Ser. No.08/630,478, filed Apr. 10, 1996, allowed.

BACKGROUND OF THE INVENTION

This invention relates to a polyimide precursor, a process for producingthe polyimide precursor, a polyimide, a process for producing thepolyimide, a photosensitive composition, a process for using thephotosensitive composition in the production of semiconductor devices,etc., and a semiconductor device and production thereof.

In semiconductor industry, inorganic materials have been used asinterlaminar insulating materials. But recently, organic materialshaving excellent heat resistance such as polyimide resins and the likeare used as interlaminar insulating materials by using their properties.

On the other hand, semiconductor integrated circuit pattern formationand circuit pattern formation on printed circuit substrates are carriedout by various complicated steps, for example, forming a film of resistmaterial on a substrate, exposing predetermined portions to light,removing unnecessary portions by etching and the like, cleaning thesubstrate surface, etc. In such a process, it is desirable to use aresist on necessary portions as it is as an insulating material afterthe pattern formation by exposure to light and development. Thus, thedevelopment of heat resistant photosensitive materials for such apurpose are demanded.

In order to meet such a demand, there are proposed heat resistantphotosensitive materials using photosensitive polyimides, ring-closedpolybutadienes, etc. as base polymers. Particularly the photosensitivepolyimides are noticed due to excellent heat resistance and easiness ofremovable of impurities.

For example, JP-B 49-17374 proposed a material comprising a polyimideprecursor and a bichromate. This material had advantages in practicalphotosensitivity and high film-forming ability, but also disadvantagesin storage stability and retention of chromium ions in the polyimide.Thus, such a material was not used practically.

In order to avoid such problems, JP-A 54-109828 proposed a process formixing a compound having a photosensitive group with a polyimideprecursor. Further, JP-A 56-24343 and JP-A 60-100143 proposed processesfor providing photosensitive groups by reacting a functional group in apolyimide precursor with a functional group in a compound having aphotosensitive group. These photosensitive polyimide precursors use as afundamental skeleton an aromatic monomer which is excellent in heatresistance and mechanical properties. But due to absorption of thepolyimide precursors per se, light transmittance in the ultravioletregion becomes low and photochemical reaction on exposed portions is notcarried out sufficiently effectively, resulting in providing problemssuch as low sensitivity and worsened pattern shape.

With recent tendency of higher integration of semiconductors, higherresolution (or smaller processing rule) is also demanded.

In order to meet such a demand, a contact/proximity exposing deviceusing a parallel light previously used is going to be replaced by a 1:1projection exposing device which is called by "a mirror projection", ora so-called "stepper" which is a reducing projection exposing device.

The stepper uses a high output oscillation line of ultra-high pressuremercury lamp and monochromatic light such as excimer laser light. As thestepper, a g-line stepper which uses a visible light (wavelength 435 nm)of g-line of ultra-high pressure mercury lamp was used mainly. But inorder to meet the demand for higher resolution, it is necessary to makethe wavelength used in the stepper shorter. Thus, the g-line stepper(wavelength 435 nm) is going to be replaced by an i-line stepper(wavelength 365 nm).

On the other hand, known photosensitive polyimide are designed for thecontact/proximity exposing device, the mirror projection exposingdevice, and the g-line stepper. But such polyimides are low intransparency and show almost no transmittance when the i-line(wavelength 365 nm) is used. Therefore, no sufficient pattern can beobtained when the i-line stepper is used.

Further, in order to meet the LOC (lead on chip) wherein a high densitymounting method of semiconductor is used, a polyimide film for surfaceprotection is required to have a thicker film thickness. When the filmthickness becomes larger, the problem of low transmittance becomesseverer.

Furthermore, a diameter of a silicon wafer becomes larger every year. Tothe contrary, a thickness of a silicon wafer has a tendency to becomesmaller. On the other hand, a thickness of a polyimide film becomeslarger every year due to the mounting method mentioned above.Accordingly, a warp of a silicon wafer having a polyimide surfaceprotective film thereon is occured due to the difference of thermalexpansivity between the polyimide film and the silicon wafer. Therefore,a photosensitive polyimide having lower thermal expansivity is stronglyrequired.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a polyimideprecursor overcoming the problems of prior art and having excellentimage forming properties, being suitable for patterning using an i-linestepper, and showing excellent mechanical properties, heat resistance,adhesiveness after thermal curing, and a process for producing the same.

It is another object of the present invention to provide a polyimide, aprocess for producing the same and a photosensitive resin compositioncontaining a polyimide precursor.

It is a further object of the present invention to provide asemiconductor device using the polyimide mentioned above, and a processfor producing the same.

The present invention provides a polyimide precursor (i.e. poly(amicacid)) having repeating units of the formula: ##STR2## wherein R¹ is atetravalent organic group; and R² is a group of the formula: ##STR3##wherein R³, R⁴, R⁵ and R⁶ are independently a hydrogen atom or amonovalent organic group, and at least two of R³ to R⁶ are independentlya monovalent organic group.

The present invention also provides a process for producing theabove-mentioned polyimide precursor which comprises reacting atetracarboxylic acid or a derivative thereof with a diamine of theformula: ##STR4## wherein R³, R⁴, R⁵ and R⁶ are as defined above.

The present invention further provides a polyimide having repeatingunits of the formula: ##STR5## wherein R¹ and R² are as defined above.

The present invention still further provides a process for producing thepolyimide mentioned above, which comprising subjecting theabove-mentioned polyimide precursor to imide ring closure.

The present invention also provides a photosensitive resin compositioncontaining the above-mentioned polyimide precursor, a semiconductordevice obtained by using the photosensitive resin composition, and aprocess for producing the semiconductor device, which comprises forminga polyimide pattern on a substrate as a mask, conducting dry etching,and subjecting to passivation processing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The polyimide precursor of the present invention has repeating units ofthe formula: ##STR6## wherein R¹ is a tetravalent organic group; and R²is a group of the formula: ##STR7## wherein R³, R⁴, R⁵ and R⁶ areindependently a hydrogen atom or a monovalent organic group, and atleast two of R³ to R⁶ are independently a monovalent organic group.

When the tetravalent organic group of R¹ in the formula (I-1) is,preferably an aromatic group, for example, a group of the formula:##STR8## mechanical properties of the resulting film are improved. Amongthem, the group of the formula: ##STR9## is more preferable.

In the formula (I-1), R² is represented by the formula (II), wherein R³,R⁴, R⁵ and R⁶ are independently a hydrogen atom or a monovalent organicgroup, and at least two of R³ to R⁶ are independently a monovalentorganic group.

When the monovalent organic groups of R³ to R⁶ are independently analkyl group preferably having 1 to 5 carbon atoms, a halogenated alkylgroup preferably having 1 to 5 carbon atoms (e.g. --CF₃, --CF₂ CF₂ H),an alkoxy group preferably having 1 to 5 carbon atoms, or a halogenatedalkoxy group preferably having 1 to 5 carbon atoms (e.g. --OCF₃, --OCF₂CF₂ H), transmittance of i-line and thermal properties of the resultingfilm are improved. Among of these monovalent organic groups, the alkylgroup is preferable.

Preferable examples of R² in the formula (I-1) are as follows: ##STR10##in order to improve light transmittance and mechanical properties andthermal properties of the resulting film.

Among them, the group of the formula: ##STR11## is more preferable.

The above-mentioned polyimide precursor can be synthesized by reacting atetracarboxylic acid or a derivative thereof with a diamine of theformula: ##STR12## if necessary in an organic solvent, preferably at-20° C. to 100° C., more preferably 0° C. to 90° C., particularlypreferably 15° C. to 50° C.

As the tetracarboxylic acid, there can be used aromatic tetracarboxylicacid such as oxydiphthalic acid, pyromellitic acid,3,3',4,4'-benzophenonetetracarboxylic acid,3,3',4,4'-biphenyltetracarboxylic acid,1,2,5,6-naphthalenetetracarboxylic acid,2,3,6,7-naphthalenetetracarboxylic acid,1,4,5,8-naphthalenetetracarboxylic acid, 2,3,5,6-pyridinetetracarboxylicacid, 3,4,9,10-perylenetetracarboxylic acid, sulfonyldiphthalic acid,m-terphenyl-3,3',4,4'-tetracarboxylic acid,p-terphenyl-3,3',4,4'-tetracarboxylic acid,1,1,1,3,3,3-hexafluoro-2,2-bis(2,3- or 3,4-dicarboxyphenyl)propane,2,2-bis(2,3- or 3,4-dicarboxyphenyl)propane, 2,2-bis{4'-(2,3- or3,4-dicarboxyphenyl)phenyl}propane,1,1,1,3,3,3-hexafluoro-2,2-bis{4'-(2,3- or3,4-dicarboxyphenoxy)phenyl}propane. Also a tetracarboxylic acidderivative of the formula: ##STR13## wherein R⁷ and R⁸ are independentlya monovalent hydrocarbon group, for example, hydrocarbyl groups such asan alkyl group having 1 to 4 carbon atoms, an aromatic group, e.g. aphenyl group; and s is an integer of 1 or more, is suitable.

Derivatives of tetracarboxylic acids include, for example,tetracarboxylic monoanhydrides, tetracarboxylic dianhydrides,tetracarboxylic chlorides, etc. As a partner of the reaction with adiamine, the use of tetracarboxylic dianhydrides is preferable from theviewpoint of reactivity. These tetracarboxylic acids or derivativesthereof can be used singly or as a mixture thereof. Among thesetetracarboxylic acids or derivatives, oxydiphthalic acid, pyromelliticacid, 3,3',4,4'-benzophenonetetracarboxylic acid and3,3',4,4'-biphenyltetracarboxylic acid are preferable.

As the diamine, those of the formula (III) are used as an essentialcomponent. It is possible to use diamines other than those of theformula (III) so far as the i-line transmittance and heat resistance arenot much lowered.

Examples of the diamines other than those of the formula (III) are4,4'-(or 3,4'-, 3,3'-, 2,4'- or 2,2'-)diaminodiphenyl ether, 4,4'-(or3,4'-, 3,3'-, 2,4'-, or 2,2'-)diaminodiphenyl methane, 4,4'-(or 3,4-,3,3'-, 2,4'-, or 2,2'-)diaminodiphenyl sulfone, 4,4'-(or 3,4'-, 3,3'-,2,4'-, or 2,2'-)diaminodiphenyl sulfide, para-phenylenediamine,meta-phenylenediamine, p-xylylenediamine, m-xylylenediamine, o-tolidine,o-tolidinesulfone, 4,4'-methylene-bis(2,6-diethylaniline),4,4'-methylene-bis(2,6-diisopropylaniline), 2,4-diaminomethylene,1,5-diaminonaphthalene, 4,4'-benzophenonediamine,bis{4-(4'-aminophenoxy)phenyl}sulfone,1,1,1,3,3,3-hexafluoro-2,2-bis(4-aminophenyl)propane,2,2-bis{4-(4'-aminophenoxy)phenyl}propane,3,3'-dimethyl-4,4'-diaminodiphenylmethane,3,3',5,5'-tetramethyl-4,4'-diaminodiphenylmethane,bis{4-(3'-aminophenoxy)phenyl}sulfone, 2,2-bis(4-aminophenyl)propane,etc. These diamines can be used singly or as a mixture thereof.

It is also possible to use aliphatic diamines such asdiaminopolysiloxanes of the formula: ##STR14## wherein R⁹ and R¹⁰ areindependently a divalent hydrocarbon group, for example, hydrocarbylgroups such as an alkylene group having 1 to 4 carbon atoms, an arylenegroup, e.g. a phenylene group; R¹¹ and R¹² are independently amonovalent hydrocarbon group, for example, hydrocarbyl groups such as analkyl group having 1 to 4 carbon atoms, an aromatic group, e.g. a phenylgroup; and t is an integer of 1 or more.

It is preferable to use the diamino-polysiloxanes in an amount of 1 to10% by weight, based on the total amount of diamines for improvingadhesiveness. When the amount is more than 10% by weight, there is atendency to lower thermal properties of the polyimide film.

It is preferable to use the diamine of the formula (III) in an amount of10 to 100% by mole, more preferably 30 to 100% by mole, based on thetotal amount of diamines. When the using amount is less than 10% bymole, there is a tendency to lower the transmittance, to lowermechanical properties and thermal properties of the polyimide film.

The ring-opening polyaddition reaction can be carried out preferably inan organic solvent such as an aprotic polar solvent which can dissolvethe produced polyimide precursor completely. Examples of such an aproticpolar solvent are N-methyl-2-pyrrolidone, N,N-dimethylacetamide,N,N-dimethylformamide, dimethylsulfoxide, tetramethyl urea, hexamethylphosphoric acid triamide, γ-butyrolactone, etc.

In addition to the aprotic polar solvent mentioned above, it is possibleto use ketones, esters, lactones, ethers, halogenated hydrocarbons, andhydrocarbons. Examples of these solvents are acetone, diethyl ketone,methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, methylacetate, ethyl acetate, butyl acetate, diethyl oxalate, diethylmalonate, diethyl ether, ethylene glycol dimethyl ether, diethyleneglycol dimethyl ether, tetrahydrofuran, dichloromethane,1,2-dichloroethane, 1,4-dichlorobutane, trichloroethane, chlorobenzene,o-dichlorobenzene, hexane, butane, octane, benzene, toluene, xylene,etc. These organic solvents can be used singly or as a mixture thereof.

The polyimide precursor of the present invention should be a compoundhaving the repeating units of the formula (I-1) in an amount ofpreferably 10% by mole or more, more preferably 30% by mole or more. Itwill be understood that the remaining repeating units have the sameformula as formula (I-1) with the exception that R² may be at least oneother divalent organic group, such as, ##STR15## each hydrogen inaromatic ring in above formulae may be substituted by an alkyl groupsuch as methyl, ethyl, propyl, buthyl, etc;

--CH₂ --; and ##STR16## wherein R⁹, R¹⁰, R¹¹ and R¹² are the same as inthe formula (V). When the content of the repeating units of the formula(I-1) is less than 10% by mole, there is a tendency to lowertransparency and mechanical strength of the resulting polyimide film.

The weight-average molecular weight (Mw) of the polyimide precursor ofthe present invention is preferably 20,000 to 100,000. When the Mw islower than 20,000, there is a tendency to lower strength of theresulting polyimide thin film. On the other hand, when the Mw is higherthan 100,000, there is a tendency for the polyimide to exhibithigh-viscosity and lower resolution. The Mw can be measured by gelpermiation chromatography using a carrier solvent such asdimethylformamide (DMF), dimethyl sulfoxide (DMSO), etc.

The polyimide of the present invention has repeating units representedby the formula: ##STR17## wherein R¹ and R² are as defined above.

Such a polyimide can be obtained by ring closure of the polyimideprecursor, usably with heating.

It is preferable to heat at 80 to 450° C. When the heating temperatureis lower than 80° C., there is a tendency to slow the ring closingreaction. On the other hand, when the heating temperature is higher than450° C., there is a tendency to deteriorate the polyimide produced.

Heating time is preferably 10 to 100 minutes. When the heating time isless than 10 minutes, there is a tendency to slow the ring closingreaction. On the other hand, when the heating time is more than 100minutes, there is a tendency to deteriorate the polyimide produced andto lower workability.

The polyimide can be used as an overcoating material on a semiconductor.

The photosensitive resin composition of the present invention comprisesa photosensitive polyamide resin which can be obtained by impartingphotosensitivity to the polyimide precursor.

As the method for imparting photosensitivity, there are a method ofintroducing an acrylic group by covalent bond into side chains (forexample, carboxylic acid groups) of the polyimide precursor, a method ofintroducing an acrylic compound having one or more amino groups by ionicbonding with carboxylic acid groups of the polyimide precursor, a methodof mixing a polyimide precursor, one or more reactive monomers, and aphotosensitivity imparting agent such as a photo acid generator, a photobase generator, etc.

Accordingly, the photosensitive polyamide resin obtained by impartingphoto sensitivity to the polyimide precursor has repeating unitsrepresented by the formula: ##STR18## wherein R¹ and R² are as definedabove; X¹ and X² are independently --COOR¹³ --CONHR¹⁴ or --COO⁻ R¹⁵⁺, inwhich R¹³, R¹⁴ and R¹⁵⁺ are independently a monovalent organic grouphaving a vinyl group.

As R¹³ and R¹⁴, there can be used an alkenyl group such as vinyl, allyl,isopropenyl, etc. As R¹⁵⁺, there may be an ammonium ion such as##STR19## wherein R¹⁶ is a alkylene group; R¹⁷ and R¹⁸ are alkyl groups.

The case of --COO⁻ R¹⁵⁺ is obtained by the method of introducing anacrylic compound having one or more amino groups by ionic bonding withcarboxylic acid groups of the polyimide precursor.

It will be appreciated that in the resin represented by the formula(I-3), some of the acid groups of the polyimide precursor may remain.

Considering easiness of volatile dispersion of photosensitive groups atthe time of thermal imide ring closure and easiness of production of thephotosensitive resin composition, it is preferable to use the method ofintroducing an acrylic compound having one or more amino groups intocarboxylic acid groups of the polyimide precursor by ionic bonding.

As the acrylic compound having one or more amino groups, there can beused N,N-dimethylaminoethyl methacrylate, N,N-diethylaminoethylmethacrylate, N,N-dimethylaminopropyl methacrylate,N,N-diethylaminopropyl methacrylate, N,N-dimethylaminoethyl acrylate,N,N-diethylaminoethyl acrylate, N,N-dimethylaminopropyl acrylate,N,N-diethylaminopropyl acrylate, N,N-dimethylaminoethylacrylamide,N,N-dimethylaminoethylacrylamide, etc. These compounds can be usedsingly or as a mixture thereof.

The acrylic compound having one or more amino groups can preferably usedin an amount of 1 to 200% by weight, more preferably 5 to 150% byweight, based on the weight of the polyimide precursor having repeatingunits of the formula (I-1). When the using amount is less than 1% byweight, there is a tendency to deteriorate photosensitivity. On theother hand, when the using amount is more than 200% by weight, there isa tendency to lower heat resistance and mechanical properties of thefilm produced.

The photosensitive resin composition may contain a photo initiator, ifnecessary.

Examples of the photo initiator are Michler's ketone, benzoin methylether, benzoin ethyl ether, benzoin isopropyl ether,2-t-butylanthraquinone, 2-ethylanthraquinone,4,4-bis(diethylamino)benzophenone, acetophenone, benzophenone,thioxanthone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexylphenyl ketone, 2-methyl-[4-(methylthio)phenyl]-2-morpholino-1-propanone,benzyl, diphenyl disulfide, phenanthrenequinone,2-isopropylthioxanthone, riboflavin tetrabutyrate,2,6-bis(p-diethylamino-benzal)-4-methyl-4-azacyclohexanone,N-ethyl-N-(p-chloro-phenyl)glycine, N-phenyldiethanolamine,2-(o-ethoxycarbonyl)oxyimino-1,3-diphenylpropanedione,1-phenyl-2-(o-ethoxycarbonyl)oxyiminopropane-1-one,3,3,4,4-tetra(t-butylperoxycarbonyl)benzophenone, 3,3-carbonylbis(7-diethylamino coumalin),bis(cyclo-pentadienyl)-bis[2,6-difluoro-3-(pyri-1-yl)phenyl]-titanium,etc. These compounds can be used singly or as a mixture thereof.

The photo initiator can be used in an amount of preferably 0.01 to 30%by weight, more preferably 0.05 to 10% by weight, based on the weight ofthe polyimide precursor having repeating units of the formula (I-1).When the amount is less than 0.01% by weight, there is a tendency tolower the photosensitivity. On the other hand, when the amount is morethan 30% by weight, there is a tendency to lower mechanical propertiesof the film produced.

The photosensitive resin composition may contain an additionpolymerizable compound, if necessary.

Examples of the addition polymerizable compound are diethylene glycoldiacrylate, triethylene glycol diacrylate, tetraethylene glycoldiacrylate, diethylene glycol dimethacrylate, triethylene glycoldimethacrylate, tetraethylene glycol dimethacrylate, trimethylolpropanediacrylate, trimethylolpropane triacrylate, trimethylolpropanedimethacrylate, trimethylolpropane trimethacrylate, 1,4-butanedioldiacrylate, 1,6-hexanediol diacrylate, 1,4-butandiol dimethacrylate,1,6-hexanediol methacrylate, pentaerythritol triacrylate,pentaerythritol tetraacrylate, pentaerythritol trimethacrylate,pentaerythritol tetramethacrylate, styrene, divinylbenzene,4-vinyltoluene, 4-vinypyridine, N-vinylpyrrolidone, 2-hydroxyethylacrylate, 2-hydroxyethyl methacrylate, 1,3-acryloyloxy-2-hydroxypropane,1,3-methacryloyloxy-2-hydroxypropane, methylenebisacrylamide,N,N-dimethylacrylamide, N-methylolacrylamide, etc. These compounds canbe used singly or as a mixture thereof.

The addition polymerizable compound can be used in an amount ofpreferably 1 to 200% by weight based on the weight of the polyimideprecursor having repeating units of the formula (I-1). When the amountis less than 1% by weight, there is a tendency to deterioratephotosensitivity including solubility in a developing solution. On theother hand, when the amount is more than 200% by weight, there is atendency to lower mechanical properties of the film formed.

The photosensitive resin composition may contain an azide compound, ifnecessary.

Examples of the azide compound are as follows. ##STR20##

These compounds can be used singly or as a mixture thereof.

The azide compound can be used in an amount of preferably 0.01 to 30% byweight, more preferably 0.05 to 10% by weight, based on the weight ofthe polyimide precursor having repeating units of the formula (I-1).When the amount is less than 0.01% by weight, there is a tendency tolower photosensitivity. On the other hand, when the amount is more than30% by weight, there is a tendency to deteriorate mechanical propertiesof the film produced.

The photosensitive resin composition may further contain a radicalpolymerization inhibitor or a radical polymerization suppressing agent,in order to enhance storage stability.

Examples of the radical polymerization inhibitor or radicalpolymerization suppressing agent are p-methoxyphenol,diphenyl-p-benzoquinone, benzoquinone, hydroquinone, pyrogallol,phenothiazine, resorcinol, ortho-dinitrobenzene, para-dinitrobenzene,meta-dinitrobenzene, phenonthraquinone, N-phenyl-1-naphthylamine,N-phenyl-2-naphthylamine, cupferron, phenothiazine, 2,5-toluquinone,tannic acid, para-benzylaminophenol, nitrosoamines, etc. These compoundscan be used singly or as a mixture thereof.

The radical polymerization inhibitor or the radical polymerizationsuppressing agent can be used in an amount of preferably 0.01 to 30% byweight, more preferably 0.05 to 10% by weight, based on the weight ofthe polyimide precursor having repeating units of the formula (I-1).When the amount is less than 0.01% by weight, there is a tendency todeteriorate storage stability. On the other hand, when the amount ismore than 30% by weight, there is a tendency to lower photosensitivityand mechanical properties of the film produced.

The photosensitive resin composition may further contain one or moreorganic solvents which are exemplified in the ring-opening polyadditionreaction to produce the polyimide precursor mentioned above. The organicsolvent can be used in an amount of 10 to 99 parts by weight, preferably20 to 97 parts by weight, more preferably 30 to 95 parts by weight, per100 parts by weight of a total of the components of the photosensitiveresin composition other than the organic solvent.

The photosensitive resin composition is coated on a substrate such as asilicon wafer, a metallic substrate, a ceramic substrate, etc. by a dipmethod, a spray method, a screen printing method, a spin coating method,etc., followed by drying with heating to remove almost of the organicsolvent to give a coated film (polyimide precursor film) having nosticking properties.

On the coated film, a mask having the predetermined pattern is formedthereon, followed by exposure to actinic light or actinic rays throughthe mask. Unexposed portions are removed by a suitable developingsolution to give a predetermined relief pattern.

The photosensitive resin composition is designed for an i-line stepper.But as the actinic light or actinic rays, there can be used acontact/proximity exposing device using an ultra-high pressure mercurylamp, a mirror projection exposing device, a g-line stepper, andultraviolet light, a visible light source, X-rays, electron beams, etc.in addition to the i-line stepper.

As the developing solution, there can be used a good solvent (e.g.N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone,etc.), a mixed solvent of the above-mentioned good solvent and a poorsolvent (e.g. a lower alcohol, water, an aromatic hydrocarbon, etc.), abasic solution (an aqueous solution of tetramethylammonium hydroxide, anaqueous solution of triethanolamine, etc.), etc.

After the development, rinsing is conducted using water or poor solvent,if necessary, followed by drying at about 100° C., to give a more stablepattern.

When the relief pattern (polyimide precursor pattern) is heated forimidization, there can be obtained a heat resistant patterned polyimide.At this time, it is preferable to heat the relief pattern at atemperature of 150° to 500° C., more preferably 200° to 400° C. When theheating temperature is lower than 150° C., there is a tendency to lowermechanical properties and thermal properties of the polyimide film. Onthe other hand, when the heating temperature is higher than 500° C.,there is a tendency to lower mechanical properties and thermalproperties of the polyimide film. Further, the heating time ispreferably 0.05 to 10 hours. When the heating time is less than 0.05hour, there is a tendency to lower mechanical properties and thermalproperties of the polyimide film. On the other hand, when the heatingtime is more than 10 hours, there is a tendency the lower mechanicalproperties and thermal properties of the polyimide film.

As mentioned above, the photosensitive resin composition can be used forforming surface protective films for semiconductors for forming apolyimide pattern as a mask which is used when an inorganic film of SiN,SiO, etc. is subjected to working such as dry etching, wet etching,etc., interlaminar insulating films for multilayer wiring boards, etc.

The semiconductor device of the present invention can be obtained byusing the photosensitive resin composition. Therefore, the semiconductordevice may have a polyimide film obtained from the photosensitive resincomposition.

The semiconductor device can be produced by using a pattern of polyimidefilm obtained from the photosensitive resin composition as a mask, andconducting, for example, passivation processing applying dry etching.

More in detail, when a film of an inorganic material such as SiO, SiN,etc. which is used to prevent chemical influences from outside andformed on wiring, is perforated by dry etching in the production of asemiconductor device, a polyimide film pattern obtained from thephotosensitive resin composition is used as a mask for dry etching. Inorder to prevent physical influences from a sealing agent, a surfaceprotective film made from polyimide is formed on the passivation film.

The present invention is illustrated by way of the following Examples.

SYNTHESIS EXAMPLES 1 TO 8

In a 100-ml flask equipped with a stirrer, a thermometer and anitrogen-introducing pipe, a diamine component shown in Table 1 andN-methyl-2-pyrrolidone were placed and stirred at room temperature undera nitrogen steam for dissolution. Then, an acid component shown in Table1 was added to the flask and stir red for 5 hours to give a viscoussolution of polyimide precursor.

The resulting solution was further heated at 70° C. for 5 hours foradjusting the viscosity to 80 poises (solid content 25% by weight) togive a solution of polyimide precursor (PI-1 to PI-8). In Table 1, usingamounts of the diamine components, the acid components andN-methyl-2-pyrrolidone are also listed.

The viscosity was measured by using a E-type viscometer (EHD type, atrade name, mfd. by TOKIMEC INC.) at 25° C. and 2.5 r.p.m.

When the solutions of polyimide precursors (PI-1 to PI-8) were dried andsubjected to measurement of infrared absorption spectra (JIR-100 type,mfd. by JEOL Ltd.) by the KBr method, the absorption of C=0 (the bondbetween carbon and oxygen) due to the amide group near 1600 cm-⁻¹ andthat of N--H near 3300 cm⁻¹ were admitted.

                                      TABLE 1                                     __________________________________________________________________________          Diamine   Acid     N-methyl-2-                                            Synthesis component component pyrrolidone                                     Example (Using amount) (Using amount) (Using amount) Polyimide                No. (g/g) (g) (g) precursor                                                 __________________________________________________________________________    1     DMAP/LP-7100                                                                            ODPA     75.0282 PI-1                                            (9.6198/0.5927) (14.7969)                                                    2 DMAP/LP-7100 ODPA/s-BPDA 74.9676 PI-2                                        (9.7610/0.6014) (7.5070/7.1198)                                              3 DMAP/3,4'-DDE/ s-BPDA 75.0411 PI-3                                           LP-7100 (14.6516)                                                             (4.7574/4.9859/                                                               0.6188)                                                                      4 TMAP/LP-7100 ODPA 74.3793 PI-4                                               (10.2745/0.5592) (13.9594)                                                   5 TMAP/LP-7100 s-BPDA 73.8293 PI-5                                             (10.5029/0.5716) (13.5336)                                                   6 4,4'-DDE/LP-7100 s-BPDA 74.976 PI-6                                          (9.5683/0.6250) (14.7987)                                                    7 OTD/LP-7100 s-BPDA 75.0261 PI-7                                              (9.9223/0.6114) (14.4750)                                                    8 OTD/LP-7100 ODPA 75.0282 PI-8                                                (9.6198/0.5927) (14.7969)                                                  __________________________________________________________________________     ##STR21##

EXAMPLES 1-5 AND COMPARATIVE EXAMPLES 1 TO 3

Uniform photosensitive resin compositions of Examples 1 to 5 andComparative Examples 1 to 3 were prepared by adding to 10 g of eachsolution of polyimide precursors (PI-1 to PI-8) obtained in SynthesisExamples 1 to 8, 0.027 g of2,6-bis(4'-azidobenzal)-4-carboxycyclohexanone (CA), 0.027 g of4,4'-bis(diethylamino)benzophenone (EAB), and 0.054 g of1-phenyl-2-(o-ethoxycarbonyl)oxyiminopropan-1-one (PDO), followed byaddition of dimethylaminopropyl methacrylate (MDAP) in an amountequivalent to the carboxyl group of the polyimide precursor, withstirring. ##STR22##

Each photosensitive resin composition solution was filtered and spincoated on a silicon wafer.

Then, using a hot plate, the coated composition was heated at 100° C.for 150 seconds to form a film of 23 μm thick. Using the resulting filmas a pattern mask, exposure to light was conducted by using an i-linestepper.

Then, the exposure film was heated at 100° C. for 60 seconds andsubjected to paddle development using a mixed solvent ofN-methyl-2-pyrrolidone/water (75/25 weight ratio), followed by heatingat 100° C. for 30 minutes, 200° C. for 30 minutes, and 350° C. for 60minutes to give a polyimide relief pattern.

A part of the resulting relief pattern was subjected to measurement ofinfrared absorption spectra by the KBr method. As a result, specificabsorption of imide was admitted near 1780 cm⁻¹.

Transmittance of the polyimide precursors (PI-1 to PI-8) obtained inSynthesis Examples 1 to 8, resolution, glass transition temperatures andadhesiveness of relief patterns thus obtained were evaluated. Theresults are shown in Table 2.

The transmittance was evaluated by spin coating a resin solution ofpolyimide precursor (PI-1 to PI-8) on a substrate (MICRO COVER GLASS,mfd. by Matsunami Glass Ind., Ltd.), drying at 85° C. for 3 minutes and105° C. for 3 minutes to give a coated film, which was subjected to themeasurement using a spectrophotometer.

The resolution was evaluated by using a through hole test pattern andmeasuring the minimum size of developable through hole.

The glass transition temperature was evaluated by coating aphotosensitive resin composition on a silicon wafer, heating at 100° C.for 30 minutes, 200° C. for 30 minutes, and under a nitrogen atmosphereat 350° C. for 60 minutes to give a coated film (film thickness 10 μm)and measuring the glass transition temperature using a TMA-1 apparatus(a trade name, mfd. by Perkin-Elmer Corp.).

The adhesiveness was evaluated by coating a photosensitive resincomposition on a silicon wafer, heating at 100° C. for 30 minutes, 200°C. for 30 minutes, and under a nitrogen atmosphere at 350° C. for 60minutes to give a coated film (film thickness 10 μm), and subjected to across cut test using a Pressure Cooker Tester (conditions: at 121° C., 2atmospheres and 100 hours).

The cross cut test was carried out by cutting 100 squares, each squarehaving a size of 1 mm×1 mm with a cutting knife, peeling with acellophane tape according to JIS K 5400, and counting the number ofretaining squares per 100 squares.

The coefficient of thermal expansion (CTE) was measured by using a TMA-1apparatus (conditions: sample size: 2×15 mm, heating rate: 10° C./min.(in air), loading weight: 10 g, CTE value: measured at 100-150° C.).

                                      TABLE 2                                     __________________________________________________________________________                          Glass                                                       Transmit-  transition                                                       Example Polyimide tance  temperature Adhesive- CTE                            No. precursor (%) Resolution (° C.) ness (ppm/° C.)           __________________________________________________________________________    Example 1                                                                           PI-1 28   6 μm (good)                                                                      300   100/100                                                                             20                                            Example 2 PI-2 23 8 μm (good) 320 100/100 18                               Example 3 PI-3 22 8 μm (good) 350 100/100 25                               Example 4 PI-4 55 6 μm (good) 330 100/100 10                               Example 5 PI-5 34 6 μm (good) 380 100/100  7                               Comparative PI-6 Less than No good 270 100/100 50                             Example 1    0.1                                                              Comparative PI-7 Less than No good 380 100/100 20                             Example 2    0.1                                                              Comparative PI-8 10 No good 300 100/100 47                                    Example 3                                                                   __________________________________________________________________________

As mentioned above, the polyimide precursor of the present invention isgood in light transmittance and suitable for preparing a photosensitiveresin composition, and shows excellent mechanical properties, thermalproperties by properly selecting substituents.

The polyimide obtained from the polyimide precursor shows excellentmechanical properties and thermal properties, e.g. excellent heatresistance.

The photosensitive resin composition of the present invention isexcellent in image formation and particularly suitable for patternformation using an i-line stepper. The polyimide pattern obtained by thephotosensitive resin composition is excellent in resolution, dimensionalaccuracy and resistance to dry etching, so that it is suitable as a maskfor passivation processing.

What is claimed is:
 1. A process for producing a semiconductor device,which comprises:(a) forming a polyimide precursor film on a substrateusing a photosensitive resin composition comprising a photosensitivepolyamide resin which is obtained by imparting photosensitivity to apolyimide precursor having repeating units of the formula: ##STR23##wherein R¹ is a tetravalent organic group; and R² is a group of theformula: ##STR24## wherein R³, R⁴, R⁵ and R⁶ are independently ahydrogen atom or a monovalent organic group, and at least two of R³ toR⁶ are independently a monovalent organic group; (b) setting up a maskhaving a pattern on a polyimide precursor film; (c) exposing thepolyimide precursor film to monochromatic light of i-line having awavelength of 365 nm, using an i-line stepper, through the mask; (d)forming a polyimide precursor pattern by removing unexposed portions ofthe polyimide precursor film, followed by heating for imidization tomake a polyimide pattern; and (e) conducting passivation processingapplying dry etching using the polyimide pattern as a mask.
 2. Theprocess according to claim 1, wherein R¹ in the formula (I-1) is a groupof the formula: ##STR25##
 3. The process according to claim 1, whereinthe monovalent organic group represented by R³ to R⁶ is an alkyl grouphaving 1 to 5 carbon atoms, a halogenated alkyl group having 1 to 5carbon atoms, an alkoxy group having 1 to 5 carbon atoms, or ahalogenated alkoxy group having 1 to 5 carbon atoms.
 4. The processaccording to claim 1, wherein R² in the formula (I-1) is a group of theformula:
 5. The process according to claim 1, wherein an amount of therepeating units of the formula (I-1) is 10% by mole or more, with theremaining repeating units having a same formula as formula (I-1) withthe exception that R² is another divalent organic group selected fromthe group consisting of: (each hydrogen in the aromatic rings in theabove formulae may be substituted by an alkyl group), --CH₂ --, and##STR26## wherein R⁹ and R¹⁰ are independently a divalent hydrocarbylgroup; R¹¹ and R¹² are independently a monovalent hydrocarbyl group; andt is an integer of 1 or more.
 6. The process according to claim 1,wherein said substrate includes a silicon wafer.
 7. The processaccording to claim 1, wherein said mask is a mask for forming a surfaceprotective film for the semiconductor device.
 8. The process accordingto claim 1, wherein said mask is a mask used for forming a polyimidepattern used as an etching mask when etching an inorganic film informing the semiconductor device.
 9. The process according to claim 1,wherein R² in the formula (I-1) is a group of the formula: ##STR27##10.10. The process according to claim 9, wherein R² in the formula (I-1) isa group of the formula:
 11. The process according to claim 1, whereinthe polyimide precursor has a weight average molecular weight in a rangeof 20,000 to 100,000.
 12. A process for producing a relief pattern,which comprises: (a) forming a polyimide precursor film on a substrateusing a photosensitive resin composition comprising a photosensitivepolyamide resin which is obtained by imparting photosensitivity to apolyimide precursor having repeating units of the formula: ##STR28##wherein R¹ is a tetravalent organic group; and R² is a group of theformula: ##STR29## wherein R³, R⁴, R⁵ and R⁶ are independently ahydrogen atom or a monovalent organic group, and at least two of R³ toR⁶ are independently a monovalent organic group;(b) setting up a maskhaving a pattern on a polyimide precursor film; (c) exposing thepolyimide precursor film to monochromatic light of i-line having awavelength of 365 nm, using an i-line stepper, through the mask; and (d)forming a polyimide precursor pattern by removing unexposed portions ofthe polyimide precursor film, followed by heating for imidization tomake a polyimide pattern.
 13. The process according to claim 12, whereinR¹ in the formula (I-1) is a group of the formula: ##STR30##
 14. Theprocess according to claim 12, wherein the monovalent organic grouprepresented by R³ to R⁶ is an alkyl group having 1 to 5 carbon atoms, ahalogenated alkyl group having 1 to 5 carbon atoms, an alkoxy grouphaving 1 to 5 carbon atoms, or a halogenated alkoxy group having 1 to 5carbon atoms.
 15. The process according to claim 12, wherein R² in theformula (I-1) is a group of the formula:
 16. The process according toclaim 12, wherein an amount of the repeating units of the formula (I-1)is 10% by mole or more, with the remaining repeating units having a sameformula as formula (I-1) with the exception that R² is another divalentorganic group selected from the group consisting of: (each hydrogen inthe aromatic rings in the above formulae may be substituted by an alkylgroup), --CH₂ --, and ##STR31## wherein R⁹ and R¹⁰ are independently adivalent hydrocarbyl group; R¹¹ and R¹² are independently a monovalenthydrocarbyl group; and t is an integer of 1 or more.
 17. The processaccording to claim 12, wherein said substrate includes a silicon wafer.18. The process according to claim 12, wherein said mask is a mask forforming a surface protective film for the semiconductor device.
 19. Theprocess according to claim 12, wherein said mask is a mask used forforming a polyimide pattern used as an etching mask when etching aninorganic film in forming the semiconductor device.
 20. The processaccording to claim 12, wherein R² in the formula (I-1) is a group of theformula: ##STR32##
 21. The process according to claim 20, wherein R² inthe formula (I-1) is a group of the formula:
 22. The process accordingto claim 12, wherein the polyimide precursor has a weight averagemolecular weight in a range of 20,000 to 100,000.